Background: An altered gut microbiota composition has recently been linked to obesity. The principal aim of this
study is to investigate and compare the gut microbiota composition in obese and lean children. Secondly,
associations between analysed gut bacterial species, dietary compounds, energy intake and biochemical blood
parameters are evaluated.
Methods: In this prospective cross-sectional study, 26 overweight/obese (mean BMI: 28.7 ± 6.5) and 27 lean (mean
BMI: 16.5 ± 2.1) children aged 6 to 16 were included. Faecal samples were collected and subjected to selective
plating and quantitative real-time PCR (qPCR) in order to determine the concentrations of bacterial species
belonging to the genera: Bacteroides, Bifidobacterium, Clostridium, Staphylococcus and Lactobacillus. Matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was applied for an in-depth
identification of species of Bacteroides fragilis group. Differences in the concentrations of gut bacterial species
between obese and lean children were statistically analysed using Mann Whitney U test. Subsequently, random
forest analysis and multiple linear regression analysis were performed in order to test associations between gut
bacterial species, dietary compounds and blood parameters.
Results: Obese children showed an elevated Firmicutes-to-Bacteroidetes ratio compared with lean children.
Furthermore, low relative proportions of B. vulgatus and high concentrations of Lactobacillus spp. were observed in
the obese microbiota. In all children, Staphylococcus spp. were positively associated with energy intake. Additionally,
in obese children, Lactobacillus spp. were positively associated with plasma hs-CRP.
Conclusions: Our findings corroborate a significant difference in the gut microbiota composition of important
bacterial species between obese and lean children. In future, non-invasive manipulation of gut microbiota
composition in early infancy could offer a new approach to manage childhood obesity and associated disorders.